Pneumatic energy absorber



2 Sheets-Sheet 1 'J. E. SNOW PNEUMATic ENERGY ABSORBER (www. m@ J M June9, 1959 Firled Dec. 19, 1955 June 9, 1959 J. E.' sNow PNEUMTIC ENERGYABSORBER 2 Sheets-Sheet 2 Filed Dec. 19, 1955 MQP JDSSH- M w W d Nm.

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m WNV 1M. m fmN NN" United States Patent 2,889,895 PNEUMATIC ENERGYABsoRBER John E. Snow, Fairborn, Ohio Application December 19,1955,Serial No. 553,818

Claims. (Cl. 18S-86) (Granted under Title 35, U.S. Code (1952), sec.266) The invention described herein may be manufactured and used by orfor Ithe Government of the United States of America for governmentalpurposes without the payment of any royalties thereon or therefor.

My invention relates to pneumatic piston drives and more particularly topulling one piston by means of driving another.

Although not limited thereto, my invention has particular usefulness inthe field of returning a piston in a drag tube to its initial startingposition such as the piston described in my copending application,Serial Number 525,754, led August 1, 1955, and now Patent No. 2,860,732.

It is well known to provide drag means for aircraft decelerationpurposes comprising a piston reciprocating in a tube wherein a piston ispulled against a predetermined constant air pressure or is pulledthrough a heavy uid such as water to provide a constant fluid frictiondrag. The problem of returning these pistons to the initial startingposition has presented diiculties to the industry. It is obvious toreturn the piston by means of a cable attached to the rear of the dragpiston which is wound on a winch or the like. However, the cost ofmaintenance and protection against weather is high and the relativelyslow operation is unsatisfactory.

It is the principal object of my invention to provide al pneumatic pullwhich will aggravatel the drag of the principal piston during itsforward operation and which will ,rapidly return the principal piston toits initial position.

It is a further object of my invention to provide a means of preventingthe inadvertent return of the principal piston.

It is a further object of my inventionl to provide electrical controlmeans for the return of the principal piston by means of the pull of asecond piston.

It is a fur-ther object of my invention to provide a piston adapted toreciprocate within a tube whereby the piston is forced to move withinthe tube in one direction by being attached at one side to an exteriorobject such as another piston and in the other direction by means of airunder pressure being introduced into the tube against the same side ofthe piston thereby pulling with it, the exterior pistons.

My means of accomplishing the foregoing objects vwill be more readilyapprehended by having reference to the accompanying drawings in which:

Figure 1 is a vertical sectional view of my pneumatic pull at initialstarting position;

'Figure 2 is a vertical view partly in section showing my pneumatic pullin the position to be returned to the initial starting position;

2 Figure 3 is a cross sectional view taken on lines 3 3 of Figure 1.

Similar numeralsrrefer to similar parts throughout the specification.

As shown in the drawings, I provide a cylinder 2 in which a piston 4 isadapted to reciprocate. I provide seal'- ICC v ing rings 6 to hold thepiston in fluid-tight relation to the inside 8 of the cylinder 2. Acable 10, which may be a 5 I provide a simple bite 14 of the cable 10bent aroundapin 16 which is inserted in a bifurcated stud 18. Not

shown in the drawings, but understood as being attached to the cable 10,may be any of the well known drag plugs or pistons referred to above.The cable may be sealed 10 at the end 20 of the tube 2 by means of agrommet 22 vinserted in a recess 24 cut into a boss 26 which isapertured at 28 to permit the passage of the cable 10. In

this form of seal a cap 30 is placed over the grommet 22 to hold it inposition. This cap 30 may be attached by being threaded into theaperture 24 or by any other suitable means. I provide a vent in the rearplate 23 as ishown.

I provide a brake indicated generally as 32 which may be attached to endof the cylinder 2 with a vibration 20 dampener 34 inserted therebetween.I provide that when the pistonv 4 has traveled forwardly through thetube 2 as far as possible, the lingers 5 and 7 may contact the innerside of a plate to prevent further passage of the piston 4. This permitsthe port 21 to remain uncovered .25 at all times.

35 reverse direction (see Fig. 2). This valve 38 may be so constructedthat it will be responsive to multiple pressure settings, if desired. Inpractice I prefer to provide that the valve 38 opens at pressure inexcess of 1,500 p.s.i. This provides a constant resistance against theforward 40 travel of the piston 4.

The only force tending to retard the passage of the piston 4 in thisdirection is the air under pressure as itescapes to the accumulator.This force aggravates the inertia of the exterior piston or whatever isattached to i end of the cable 10. lf it is an exterior drag the other-piston, the force exerted against the travel of the piston augments thedrag and is considered benelcial.

As shown in Figure 1, by closing the switch 74 the solenoid valve 78,which is normally closed, is opened and air under pressure is permittedto pass from the accumulator 40 through pipe 36 to port 21 into the tube'2 to bear against the forward side of the piston 4 and force itsmovement in a lateral direction. Of course, the pressure from theaccumulator 40 may be controlled by a multiple setting switch, ifdesired.

If it is desired to vent the air in the tube 2 to permit lrepairs or forany other reason, theA switch 72 may be closed and the solenoid valve94, which is normally closed, will `open and vent the air in the tube 2.As shown in the drawings, I have provided a selfenergized brake 32 toprevent inadvertent lateral movei "ment of the cable 10 after the piston4 has traveled forwardly down the tube 2.

In the brake 32 I provide a pair of brake shoes 42 and 44 which havetapered shoulders 54 and 56 as shown Ain the drawings. The taperedshoulders 54 and 56 ride :against rollers 58 set in slots 59 held bypins 61 in the brake housing 33. The brake shoes 42 and 44 havelongitudinal grooves 46 and 48 which are lined with brakev linings-50and 52 and are adapted to engage the cable 10 as shown in Figure 3. Iprovide that the brake shoes 42 and 44 embracev the cable 10 in asutliciently rm Pad-termed June 9, 1959 p 3 manner so that if the cablemoves backwardly, the brake shoes 42 and 44 move forwardly a shortdistance against the rollers 58 and cramp the cable 10 to preventfurther movement. This is accomplished by the brake shoes 42 and 44moving in the direction of the force against the piston 4 carried by thecable 1G. The tapered shoulders 54 and 56 are forced by the rollers 58tol cramp the cable 10 in such a manner that the cable 10l 4is preventedfrom any further travel in that direction. Thus I have provided aself-energized brake which holds the piston 4 against inadvertentreturn.

In order to free the cable 10 when desired, I provide pistons 60 and 62inside of cylinders 64 and 66 connected to the brake shoes 42 and 44respectively by rods 68 and 70. By means of appropriate piping `asshown, I provide that air may be introduced at the forward side of thepistons 60 and 62 to force the brake shoes 42 and 44 to free the cable10. I accomplish this when the switch 74 is closed. Besides opening thevalve 78,-v it opens a normally closed valve 76 as shown in Figure il.The valve 76 is a normally closed three-way solenoid valve and isintended to permit air under pressure to pass from the accumulator 40Vin the same manner as valve 78 when the switch 74 is closed. When thevalve 76 is closed (the switch 74 being open) no air is permitted topass to the pipes 80 and 82. When the switch 74 is closed, the valve 76permits air to pass from the accumulator 40 through the pipes 80 and 82thereby forcing the pistons 60 and 62 to move rearwardly, unseating thebrake shoes 42 and 44. The valve 76 is so constructed that when it isclosed to prevent air from passing through it from the accumulator 40,the pipes 80 and 82 are vented to the atmosphere through it.

If it is desired not to depend upon the self-energized features of mybrake 32, I provide electric means to kick-in the brake should the cable10 move rearwardly before desired. As shown in Figure 2, I provide acentrifugal switch 92 which may be any of the well known ball governors.I have shown schematically a simple rotating ball governor switch 92which is normally opened when the cable is at rest. The arrangementshown in Figure 2 includes an idler wheel 96 in contact with the cable10. I provide that the idler wheel 96 contains an override clutch whichfrees the wheel 96 from turning the shaft 9S except when the cable 10moves in a rearward direction. The shaft 98, when engaged, rotates thegears 99 which in turn rotate a governor 100. As the balls rise due toany return movement of the cable 10, the contacts 102 which are normallybelow the contact 104, move upwardly and mate with the contact 104thereby opening a three-way solenoid valve 90 (similar to valve 76)which instantly passes air from the accumulator 40 to the rear of thepistons 60 and 62 through the pipes 84 and 86. This will cause the brake32 to set and prevent further movement of the cable 10. The cessation ofmovement of the cable 10 will cause the contacts 102 to fall out ofcontact and the system will vent when the three-way solenoid valve 9i)goes normally closed. The venting of the three-way solenoid valve 9@relieves the air pressure in pipes 84 and 86, similar to the operationof valve 76 as set forth above.

In order that the governor switch 92 does not operate to energize thebrake 32 during the retraction of the piston 4 when it is desired toforce the piston 4 in a rearward direction through tube 2,v I providethat the electric switch 74 is so constructed that when it is closed inorder to open the valve 78 and the Valve 76 to force the retraction ofthe piston 4 and the release of the brake 32, no current is supplied tothe governor switch 92` and consequently even though it calls for theopening of valve 90, there is no current supplied for this purpose.HoW-' ever, on the other hand, when the switch 74 is thrown from itsclosed position over to the opposite position, it is clear that currentwill ow to the governor`92 and it thereby becomes energized and preventsthe rearward movement of the cable 10.

I have set forth the details of my invention which provides pretensionforce on the cable 10 when it is in the position shown in Figure 1 andalso permits the prepositioning of any drag, plug, or the like that maybe attached to the other end of the cable 10. By adjusting the airpressure in the tube 2, I am able to position the piston 4 as desiredalong the tube 2 which will provide the pretensioning and thepre-positioning features described above.

Since I have provided both electrical and self-energized braking means,I have provided a fail-safe system that quickly will retract any drag orplug presently in use. For example, I have found in practice that with atube of approximately two inches (2) in diameter several hundred feetlong, I am able by means of my invention to retract in twenty seconds, adrag plug that has traveled two thousand feet in its tube resistingthirty million foot pounds of energy.

My device described above has the added Afeature of being temperaturecompensated since it accommodates for elongation of the cables due tothermal expansion or contraction. The system is also capable of beingpreset with multiple pressure settings from the accumulator 46 asdescribed above.

Of course the system will perform satisfactorily without the brakegovernor and may be operated without any brake mechanism if desired.

Having described my invention what I regard as new and desire to protectby Letters Patent is:

1. A pneumatic pull comprising a cylinder adapted to be substantiallyairtight, a piston adapted to reciprocate in said cylinder, said pistonconnected to means to pull it forwardly through said cylinder, means toforce said piston in the opposite direction in said cylinder, said lastrnamed means including means adjacent the forward end of said cylinderfor introducing air under pressure into said cylinder to move saidpiston in said opposite direction and means automatically engageablewith the piston connected pull means lto prevent further travel of saidpiston in said opposite direction once it comes to rest after itsforward movement in said cylinder, said means for preventing furthertravel of said piston in said opposite direction after its forwardmovementhas ceased comprising a self-energizing brake formed of aplurality of brake shoes adapted to clamp said pull means and toj wedgesaid pull means to prevent further movement of said pull means in saidrearward direction when said piston moves in said opposite directionafter ceasing its forward movement, wherein the brake is electricallyinitiated to wedge said pull means, said electrical initiating meanscomprising an energizing circuit, switch means in said circuit foropening and closing said circuit, a 'centrifugal switch in saidenergizing circuit actuated by said pull means, said switch adapted tobe normally open when said pull means is at rest, said switch connectedelectrically when closed to an electrically operated valve in a pipingsystem, said valve responsive to current in said energizing circuit fromsaid centrifugal switch and adapted to open to pass air under pressurefrom an outside source to a plurality of tubes in the rear of aplurality of pistons adapted to reciprocate in said tubes, said pistonsconnected to said brake shoes and adapted to force said brake shoes towedge said pull means, and electrical means to release said air underpressure'in the rear of said plurality of pistons whereby said brake isloosened from said pull means.

2. In a pneumatic pull device, a cylinder having av fixed forward endclosure and a fixed rear end closure, a piston reciprocatable in saidcylinder, elongated flexible pull means connected to saidr piston andextending through lsaid forward end closure to pull said piston fromsaidV rear end-closure forwardly toward said forward endclosureandcontrolmovement of said piston from said forward end closuretoward said rear end closure, pressure uid supply means, conduit meansconnecting said pressure supply means to the forward end of saidcylinder, a luid pressure accumulator in said conduit means connected tosaid pressure supply means for supplying pressure uid into the forwardend of said cylinder to move said piston toward said rear end closureand receive pressure uid from said cylinder when said piston is pulledforwardly toward said forward end closure of said cylinder by saidelongated exible pull means, clamping means at the forward end of saidcylinder, movable into and out of clamping engagement with saidelongated flexible pull means, pressure operated means connected to saidconduit means for moving said clamping means into clamping engagementwith said elongated flexible pull means to control movement of saidpiston and pull means toward said rear end closure of said cylinder,pressure operated release means connected to said conduit means formoving said clamping means to relieve clamping pressure thereof on saidelongated exible pull means, means for selectively controlling saidpressure operated means and said pressure operated release means, checkvalve means in said conduit means between said pressure accumulator andsaid cylinder opening toward said pressure accumulator, said conduitmeans including a bypass conduit around said check valve means connectedbetween said pressure accumulator and said cylinder, valve means in saidbypass conduit means, separate uid pressure operated means connected tosaid clamping means for moving said clamping means into and out ofclamping engagement with said elongated flexible pull means, separateconduit means connected between said pressure accumulator means and eachof said separate uid pressure operated means, separate valve means ineach of said separate conduit means for controlling pressure Huid fromsaid accumulator to each of said separate uid pressure operated meansfor selectively controlling said clamping engagement of said clampingmeans on said elongated flexible pull means for controlling movement ofsaid piston and pull means in said cylinder between said end closures.

3. Apparatus as claimed in claim 2, including electrically operableactuating means for said valve means, and switch means therefor forsimultaneously actuating said separate valve means to admit pressure uidfrom said pressure accumulator to the forward end of said cylinder tomove said piston toward said rear end closure and to admit pressurefluid from said pressure accumulator to said separate fluid pressureoperated means for moving said clamping means to relieve the clampingengagement thereof on said pull means to permit movement of said p'istonfrom said forward end of said cylinder toward said rear end of saidcylinder under the influence of pressure uid in said cylinder.

4. In a pneumatic pull device, comprising an elongated cylinder having aclosed rear end and a closed forward end, a piston reciprocatable insaid cylinder between said forward end and said rear end, means forsupplying uid pressure to said cylinder adjacent said forward end formoving said piston toward said rear end, an elongated flexible pullmember connected to said piston and extending longitudinally throughsaid cylinder and said forward end for moving said piston from said rearend toward said forward end, packing gland means between said pull meansand said forward end for preventing escape of pressure uid between saidpull means and said forward end, self energizing clamping means disposedin front of said forward end for braking engagement with the oppositesides of said pull means incident to movement of said piston and pullmeans toward said rear end of said cylinder, fluid pressure operatedmeans connected to said self energizing clamping means for moving saidself energizing clamping means to release position to release said pullmeans, a pressure accumulator adapted to be supplied with a pressurelluid at a predetermined pressure, a first pressure conduit establishingcommunication between said accumulator and said cylinder in the forwardend thereof, check valve means in said conduit opening toward saidaccumulator, a second conduit in communication between said accumulatorand said forward end of said cylinder bypassing said first pressureconduit, valve means in said second conduit for controlling delivery ofpressure fluid from said accumulator into said cylinder between saidforward end and said piston, a third conduit means connected incommunication between said accumulator and said fluid pressure operatedmeans for releasing said self energizing clamping means, separate vvalvemeans in said third pressure conduit means for controlling uid pressurebetween said accumulator and said fluid pressure operated means forreleasing said clamping means, and valve actuating means for openingsaid last mentioned valve means while said piston is in the forward endof said cylinder to disengage said clamping means and admit uid pressureto said cylinder to move said piston and pull means toward said rear endof said cylinder.

5. Apparatus as claimed in claim 4 including second uid pressureoperated means for urging said self energizing clamping means towardself energizing clamping engagement with said pull means, la fourthpressure conduit connected between said accumulator and said secondiluid pressure operated means for supplying operating fluid pressurethereto, independently of the other conduit means, valve means in saidfourth pressure conduit means normally closing said fourth conduitmeans, speed responsive means engaging said pull means and operable toopen said last Valve means during movement of said piston and said pullmeans toward said rear end of said cylinder at a speed in excess of apredetermined nate of travel of said piston to engage said clampingmeans with said pull means to limit the rate of travel of said pistonand pull means toward said closed end of said cylinder.

References Cited in the le of this patent UNITED STATES PATENTS 787,374Graham Apr. 18, 1905 840,877 Steedman Jan. 8, 1907 1,956,110 TurrettiniApr. 24, 1934 2,001,988 Temple May 21, 1935 2,632,425 Grover Mar. 24,1953 2,765,054 Rossman Oct. 2, 1956 2,767,601 Reed Oct. 23, 1956 FOREIGNPATENTS 1,077,611 France May 5, 1954

